A pest weed dumped in the Wairakei Stream could take years to eradicate, and residents say it's an eyesore.

The Ministry for Primary Industries, which was working alongside the Tauranga City Council to eradicate salvinia, said it could take until 2021 or 2022 to clear.

Some residents that have properties on Parton Rd beside the stream told the Bay of Plenty Times they commended the project to eliminate the weed, which was discovered earlier this year, but the stream and debris beside it looked awful.

Pam Spraggon said a big mess had been left behind and the surrounding area including the foliage that ''looks dead and revolting''.

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Carol Pilgrim said the water was dirty brown and, in her view, more salvinia was growing.

''I think I saw small clumps of it.''

Her husband James said ''down here it is just a mess''.

Fellow neighbour Byron Glendon said the tape used to close off the area was off-putting.

An MPI spokesperson said it must remove every remaining piece of salvinia because small fragments could survive and grow.

It suspected the plant may have been transferred to the stream from an aquarium or pond.

''These actions can cause major impacts on the infested waterway, as we have seen at Wairakei Stream.''

To date, MPI had removed virtually all the salvinia plants while the Tauranga City Council had sprayed herbicide on the banks and scrub near the stream.

Workers would continue to monitor the stream until they were confident they had eradicated salvinia, she said.

''We will continue our weekly inspections for several months after we stop finding plants. This could be a few weeks or months.''

''Once the stream has been free of plants for several months we can go to the final phase of the eradication programme. The monitoring phase will be for a further two-three years.''

The waterway would continue to be regularly checked during this time but less frequently, and MPI said it was unlikely the weed would have had any impact on the wildlife.

Meanwhile, Tauranga City Council would clear the debris near Parton Rd next week or when it was dry enough to get a vehicle into the area safely.

Tauranga City Council Drainage Services team leader Wally Potts said it was manually removing any plants while MPI was paying for the cost of the removal.

The cost to remove the salvinia was not available at edition time. The Bay of Plenty Times has lodged an Official Information Act request to MPI requesting the information.

The Details
* Salvinia molesta (salvinia) is known worldwide for its fast spread and significant impacts on lakes and waterways.
* It forms dense mats on the water surface and has the potential to destroy the habitat of native plants and animals, including native aquatic birdlife.
* Attracts breeding mosquitoes, removes oxygen from the water, affects recreational activities and creates a drowning risk for people and animals.
* If you have salvinia on your property, please call MPI pest and disease hotline 0800 80 88 66, and we will arrange for the plants to be disposed of safely.